Strap-stretching device



W 1944" J. H. BRAMBLE 2,349,608

STRAP- STRETGHING DEVICE Filed May 20, 1943 2 Sheets-Sheet 1 wrmzssss: INVENTORV ATTORNE J. H. BRAMBLE 2,349,608 STRAP-STRETCHING DEVICE Filed May :20, 1943 2 Sheets-Sheet 2 34 In 3 2.9 f I w WW I 26 L i I -25 a WITNESSES: I INVENTOR I "70/772 HBmmbZe.

ATTOR Patented May 23, 1944 STRAP-STRETCHENG DEVICE John H. Bramble, Sharpsville, Pa, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a. corporation of Pennsylvania Application May 20, 1943, Serial No. 487,797

8 Claims.

My invention relates to devices for stretching or tightening straps or bands of metal about a substantially solid mass and for maintaining a predetermined tension on the strap or band until it is fastened. The invention is adaptable for applying steel bands about core structures of transformers where it is desirable to apply the band under a predetermined tension to maintain a continuous predetermined pressure on the core parts.

Devices for stretching or tightening a strap or band around a box or package are known, but generally these articles are compressible and there is no particular reason for maintaining a predetermined tension of the band. When the article enclosed by the strap or band is compressible, no rapid increase in the tension on the band takes place upon operation of the stretching device. However, when a solid article, such as the iron core of a transformer, is to be enclosed within a metal strap under a predetermined tension, it becomes necessar to provide for controlling this tension, since a relatively slight stretching of the strap beyond its desired value will greatly increase the stresses on it, and failure to bring the strap to the desired tension will cause it to fail in its purpose of maintaining a desired force on the parts of thecore.

In a copending application of John K. Hodnette, Serial No. 377,472, filed February 5, 1941, for Electrical induction apparatus, a core and coil assembly for transformers is disclosed in which the core parts are formed of loops of magnetic material wound layer upon layer and bonded together. The loops are cut to form two U- shaped core portions which are assembled about the coils of the transformer and held in place by metal bands surrounding the core loops. The band or strap is placed about the core loop and drawn to a predetermined tension and fastened in place to maintain a predetermined pressure upon the butt joints of the core loops. With the ordinary tool employed for stretching the band about the usual type of articles, it is difiicult to apply the desired pressure because a very slight increase in the stretch of the band about the solid mass of iron greatly increases its tension. If this tension is too great, the band will break. If it is not great enough, the band will not maintain the desired pressure on the butt joint.

It is an object of the present invention to Drovide a strap-stretching device that will bring the strap to a desired tension about a solid article and will not increase the tension above the desired amount.

Other objects and advantages of the invention will be apparent from the following description of a preferred embodiment of the invention, reference bein had to the accompanying drawings, in which:

Figure 1 is an elevational view of a core loop with the strap-stretching device applied for stretching a steel strap about the loop;

Fig. 2 is an enlarged side elevaticnal View of the device shown in Fig. 1;

Fig. 3 is a side elevational view of a portion of the strap-stretching device with a part of the casing removed to illustrate the operating mechanism;

Fig. 4 is a top plan view of the strap-stretching device; and

Fig. 5 is a detailed sectional view taken on the line V-V of Fig. 4.

Referring to the drawings, and particularl to Figs. 1 and 2 thereof, the tool I is shown in position for applying a, strap about a core loop comprising two U-shaped portions 2 and 3 for maintaining a predetermined pressure at the butt joint surfaces 4 between the two U-shaped core portions. Referring to Fig. 1, the strap 5 is shown having one end 6 extending over the corner of the core and extending along the surface of the loop under a clip 1 and bent at 8 to extend through the clip 1 which surrounds the strap, the strap continuing, as shown at 9, over the end portion 6 and about the core loop, and extending about the core loop, the other end portion H of the strap extending also through the clip 7 and positioned so as to be gripped by the tool for tightening about the core loop. The clip 1 is a steeve or band of metal about the two ends of the strap 5, when the strap is pulled tight is crimped to deform the edges of the steeve and of the ends of the strap passing therethrough to fasten them in a well known manner.

The tool comprises a frame member l2 formed integrally with a handle 13 and including a casing section I4 normally secured to the casing by screws IE to form a unitar part thereof. The casing is provided with a lower flat surface l6 extending horizontally at the lower surface of the complementary frame portions l2 and H5 in a plane substantially parallel with the direction of the handle l3. The lower forward portion of the casing section I 4 is provided with a foot or flange I'l projecting laterally therefrom and which extends horizontally above the surface of the article about which the steel band is to be stretched to form a gripping member cooperating with the pivoted gripping member l8 mounted on a pivot pin I9 and secured in place by a setscrew 22. One end II of the strap 5 is adapted to lie in contact with the foot or flange I1 and to be engaged by the serrated gripping surface 23. The gripping member I8 is normally moved into engagement with the strap II by means of a coil spring 24 which engages a recess 25 formed in the gripping member and bears against a flange 26 formed in the casing I4. It will be noted that the position of the gripping member I8 is such that as the strap II is pulled toward the left, as viewed in Fig. 2, it tends to tighten the grip of the member I8 on the strap and to press it more tightly against the foot or flange H.

The casing members I2 and I4 are provided with a horizontal guideway 21 adapted to accommodate a rack bar 28 which is formed at one end with an enlarged head 29, and which may be provided with a detachable screw 3I for retaining the rack bar in its guideway. The head 29 may g be provided with gripping members similar to the members I! and I8, but, as disclosed, are shown as provided with a foot or flange member 32, which is positioned below the end I I of the metal strap, and an upper member 33 positioned above about the core loop. The mechanism for effecting this operation comprises a pinion 36 which measures with the teeth of the rack bar 28 and which is mounted on a shaft 31 having bearings inthe opposite Walls of the casing sections I2 and I4. The hub of the pinion 36 carries an integrally formed ratchet wheel 38 by which the pinion is rotated, and the teeth 39 of the ratchetwheel are adapted to be engaged by a pawl 42 which is located within the chamber of the casing members I2 and I4, and pivotally connected by a pin 45 with an operating lever 46, which is pivotally mounted on a pin 41 carried by the casing members. The upward movement of the lever 46, from the position illustrated in Figs. 2 and 3 'causethe pawl 42 to move downwardly and eifects rotation of the ratchet wheel 38 and the pinion 36, the pawl 42 being'normally moved into engagement with the ratchet teeth by the spring 48.

The spring 48 is mounted about apin 49, the lower end of which engages a socket 5| formed in the upper side of a detent 52 which is pivoted on a pin 53 mounted in the casing. The detent 52 is provided with a tooth 54 adapted to engage the teeth 39 of the ratchet wheel to prevent reverse rotation thereof. The upper end of the pin 49 is positioned within a socket 55 in a projecting head 56 forming a part of the pawl 42. The lowerend of the spring 48 engages a collar 51 mounted on the pin 49 and the upper end of the spring 48 engaging the projecting head- 56, When thepawl 42 is operated to rotate the ratchet wheel 38, the detent 52 rises over the teeth of the ratchet'wheel and engages a tooth in a new position to hold the ratchet wheel against reverse rotation durin a reverse movement of the pawl 42.

To permit the release of the ratchet wheel and to allow a relative return movement of thehead 29 and the rack bar 26 after these parts have been aotuated to efiect the desired stretching of the steel band 5, the detent 52 is moved upwardly about its pivot 53 and the pawl 52 is simultaneously moved out of engagement with the ratchet teeth 39. This operation is effected by a releasing member 68 mounted on a shaft 6| and provided with a projection 62 adapted for engaging the underside of the detent 52 and also with an upwardly extending part 63 which serves as a cam to effect movement of the pawl 42 away from engagement with the teeth 39 of the ratchet wheel. A lever 64 is provided for rotating the shaft 6I in a clockwise direction to eifect the release of the pawl 42 and the detent 52 from engagement with the teeth of the ratchet wheel 38.

In order to provide for limiting the pressure or tension to be applied to the steel strap 5, a second lever I8 is provided mounted upon a pin II at the outer or movable end of the lever 46 and extending inwardly along the lever 46. The levers 46 and I8 are mounted directly below the handle I3, so that the lever I8 and the handle I3 together provide hand grips whereby the two levers I8 and 46 may be moved upwardly by the fingers engaging the finger grooves 13. A rack I4 is provided extending downwardly from the handle I3 and provided with teeth I5 on the inner side thereof adjacent the outer end of the lever 46. A spring member I6 is shown mounted on the lever 46, as by rivets I1, and adapted to engage the lever I8. An adjusting screw I8 is provided having a nut I9 associated therewith for varying the position of the spring I6.

A locking member 8| is shown positioned on the outer end of the lever 46, and slidably attached thereto by screws 82 extending through slots in the member 8i, to permit the member to move under the force of a spring 83. One end of the spring 83 is engaged by a fixed abutment 84 mounted on the lever 46 and the opposite end engages an abutment 85 extending outwardly from the body portion of the locking member 8|. The outer end 86 of the locking member 8| is adapted to engage between the teeth I5 of the rack 14, but is normally held in its illustrated position by a latch member 81 mounted on the lever 86 by the pin 88 and engaging one side of the abutment 85.

'A pin 89 extends from the lever 18 through an opening in the lever 46 to engage the latch 81. h

After the steel band has been positioned about the core loop, as shown in Fig; 1, the members I! and I8 gripping the end II thereof and the members 32 and 33 engaging the end of the clip I, a continued up and down movement of the levers I8 and 46 by a repeated gripping or closing of the hand about the'handle I3 and the lever 70 causes the ratchet wheel to move in the above-described manner to operate the rack bar 28 so as to move the head 29 toward the left or away from the main body of the device, thus drawing the steel strap 5 about the core loop. As this operation continues until the tension of the strap increases, the amount of force on the lever 18 necessary to move the lever 46 to cause movement of the ratchet wheel and of the rack bar increases with the tension on the strap. The force from the lever I8 which is gripped by the fingers, is applied to the lever 46. through the spring I6 which flexes with the increase in force being applied, so that with the increase in applied force, the lever I8 moves closer to the lever 46 with each successive upward movement thereof. The setscrew I8 is so adjusted that atthe'desired tension it must be applied to the steel strap. The upward movement of the lever I8-with respect to the lever 43 will move the pin 89 sufliciently to release'the latch BI'andpermit; the locking member 8| to be forced by the spring 83 between the teeth 15 in the rack member of the device to thus lock the device against further operation and to thus prevent further increase in the tension on the strap 5. With the stretching tool in this position, another tool is thenapplied to the clip I to crimp the clip in a well known manner, so as to lock or permanently fasten the ends of the strap in its permanent position. The lever 64 is then operated as above-described to release the ratchet wheel for reverse movement, thus permitting the head 29 to move toward the main frame member, so that the end H of the strap moves to the right with respect to gripping member I8, thusreleasing the grip and permitting separation of the tool from the strap.

It will. be understood by those skilled in the art that modifications maybe made in the details of the structure illustrated and described without departing from the spirit of my invention, and it is intended that the above description of a preferred embodiment of the invention be taken in an illustrative and not in a limiting sense.

I claim asmy invention:

1. The combination in a strap-stretching device, of a pair of relatively movable members, means carried by each of said relatively movable members and constructed to grip the ends of a flat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from ecah other for drawing said strap taut around an article and maintaining said overlapping portions in taut condition, said means comprising a manually operable lever for applying a force for moving said relatively movable members and a single locking means operable upon the application of a predetermined force by said lever for locking said lever against further movement in either direction.

2. The combination in a strap-stretching device, of a frame, a rack bar having movement in said frame, means carried by said bar and additional means mounted on said frame for separately engaging the opposite ends of a strap with the ends overlapping one above the other, means carried by said frame including a ratchet wheel for effecting movement of said rack bar relative to said frame, a pawl adapted to engage said ratchet wheel, a handle mounted in fixed position on said frame, operating means movable with respect to' said handle for effecting a reciprocating movement of said pawl, means for applying force to the operating means including a lever and a calibrating spring, and a single locking means operated upon the application of a predetermined force to the operating means for locking the operating means against further movement in either direction.

3. The combination in a strap-stretching device, of a pair of relatively movable members, means carried by each of said relatively movable members and constructed to grip the ends of a flat metal strap with said ends overlapping one above the other, and means. for moving said relatively movable members away from each other for drawing said strap taut around an article and maintaining said overlapping portions in taut condition, said means including a lever pivotally mounted on said device, a second lever mounted on the first-named lever, biasing means between said two levers through which force applied to the second-named lever is transmitted to the first-named lever for operating the stretching device, said biasing means being effective for varying the relative positions of the two levers with variations in the force transmitted, and a single locking means for interrupting further movement of the first-named lever upon the application of a predetermined force thereto.

4. The combination in a strap-stretching device, of a pair of relatively movable members, means carried by each of said relatively movable members and constructed to grip the ends of a fiat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for drawing said strap taut around an article and maintaining said overlapping portions in taut condition, said means including a lever pivotally mounted on said device, a second lever pivotally mounted on the outer end of the first-named lever and extending inwardly along the first named lever, biasing means between said two levers through which force applied to the secondnamed lever is transmitted to the first-named lever for operating the stretching device, said biasvice, of a frame, a rack bar having movement insaid frame, means carried by said bar and said frame for engaging a strap, means carried by said frame including a ratchet wheel for effecting movement of said rack bar relative to said frame, a pawl adapted to engage said ratchet wheel, a handle mounted in fixed position on said frame, operating means movable with respect to said handle for effecting a reciprocating movement of said pawl, said means including a lever pivotally mounted on said device, a second lever mounted on the first-named lever, biasing means between said two levers through which force, applied to the second-named lever, is transmitted to the first-named lever for operating the stretching device, said biasing means being effective for varying the relative positions of the two levers with variations in the force transmitted, and locking means for interrupting further movement of the first-named lever in either direction upon the application of a predetermined force thereto through the second named lever.

6. The combination in a strap-stretching device, of a frame, a rack bar having movement in said frame, means carried by said bar and said frame for engaging a strap, a handle mounted in fixed position on said frame, means carried by said frame including a ratchet wheel for effecting movement of said rack bar relative to said frame, a pawl adapted to engage said ratchet wheel, operating means movable with respect to said handle for effecting a reciprocating movement of said pawl, said means including a lever pivotally mounted on said device, a second lever pivotally mounted on the outer end of the firstnamed lever and extending inwardly along the first-named lever. biasing means between said two levers through which force applied to the second-named lever is transmitted to the firstnamed lever for operating the stretching device, said biasing means being effective for varying the relative positions of the two levers with variations in the force transmitted, and a single locking means for interrupting further movement of the first-named lever upon the application of a predetermined force thereto.

7. The combination in a strap-stretching device, of a frame, a pair of relatively movable members supported on said frame-means carried by each of said relatively movable members and constructed to grip the ends of a flat metal strap with said ends overlapping one above the other, and means for moving said relatively movable members away from each other for drawing said strap taut around an article and maintaining said overlapping portions in taut condition, said means comprising a lever pivotally mounted on the frame of said device, a second lever pivotally mounted on the outer end of the firstnamed lever and extending inwardly along the first-named lever, a locking rack extending adjacent the path of movement of the outer end of the first-named lever, a locking member mounted on said first-named lever and positioned for movement into engagement with said locking rack, means biasing said locking member into engagement with said locking rack, and latching L means for normally retaining said locking means out of engagement with said locking rack, biasing means between said two levers through which force applied to the second-named lever is transmitted to the first-named lever for operating the stretching device, said biasing means being effective for varying the relative positions of the two levers with variations in the force transmitted between them, and means operable upon the transmission of a predetermined force between 1 the two levers for releasing the latching means for permitting operation of said locking member to engage said locking rack and prevent further operation of said lever. Y

8. The combination in a strap-stretching device, of a frame, a rack bar having movement in said frame, relatively movable means carried by said bar and by said frame for engaging a strap, means carried by said frame including a ratchet wheel for effecting movement of said rack bar relative to said frame, a pawl adapted to engage said ratchet wheel, a handle mounted in fixed position on said frame, an operating lever pivotally mounted on the frame of the device, a second lever pivotally mounted on the outer end of the first-named lever and extending inwardly adjacent the first-named lever, a rack extending adjacent the path of movement of the outer end of the first-named lever, a locking member mounted on said first-named lever and positioned for movement into engagement with said rack, means biasing said locking member into engagement with said rack, and latching. means for normally retaining said locking member out of engagement with said rack, biasing means between said two levers through which force applied to the second-named lever is transmitted to the firstnamed lever for operating the strap-stretching device, said biasing means being effective for varying the relative positions of the two levers with variations in the force transmitted, and means operable upon the transmission of a predetermined force between the two levers for releasing the latching means for permitting operation of said locking member to engage said rack and prevent further operation of said lever.

JOHN H. BRAMBLE. 

